Wildfire is an important ecological process that influences species’ occurrence and biodiversity generally. Its effect on bats is understudied, creating challenges for habitat management and species conservation as threats to the taxa worsen globally and within fire-prone ecosystems. We conducted acoustic surveys of wildfire areas during 2014–2017 in conifer forests of California’s Sierra Nevada Mountains. We tested effects of burn severity and its variation, or pyrodiversity, on occupancy and diversity for the 17-species bat community while accounting for imperfect detection. Occupancy rates increased with severity for at least 6 species and with pyrodiversity for at least 3. Two other species responded negatively to pyrodiversity. Individual species models predicted maximum occupancy rates across burn severity levels but only one species occurred most often in undisturbed areas. Species richness increased from approximately 8 species in unburned forests to 11 in pyrodiverse areas with moderate- to high-severity. Greater accessibility of foraging habitats, as well as increased habitat heterogeneity may explain positive responses to wildfire. Many bat species appear well adapted to wildfire, while a century of fire suppression and forest densification likely reduced habitat quality for the community generally. Relative to other taxa, bats may be somewhat resilient to increases in fire severity and size; trends which are expected to continue with accelerating climate change.

Abstract. Non-linear and interacting effects of fire severity and time since fire may help explain how pyrodiversity promotes biodiversity in fire-adapted systems. We built on previous research on avian responses to fire by investigating how complex effects of burn severity and time since fire influenced avian community composition across the northern Sierra Nevada, California. We conducted avian point counts from 2009 to 2015 in 10 fires that burned between 2000 and 2014, resulting in a chronosequence of 1-15 yr post-fire. We estimated the effects of burn severity, time since fire, non-linear and interacting effects of fire severity and time since fire, pre-fire forest conditions, and several physiographic parameters on the density of 44 breeding bird species using hierarchical distance sampling models. In addition, we fit separate models to observations of each species in unburned forest to compare species' densities between burned and unburned forests. At least one of the non-linear or interaction fire effects was significant for 27 (61%) of the 44 bird species. The quadratic effect of time since fire was an important predictor of post-fire densities of 20 species, illustrating the dynamic nature of this post-wildfire avian community. Greater maximum densities were estimated at some combination of burn severity and time since fire than in unburned forest for 13 of the 44 (30%) species, only one of which reached maximum density following low-severity fire. In contrast, all of the 12 species that were more abundant in unburned forest reached maximum post-fire densities in fires that burned at low severity. Results from the study suggest that consideration of the non-linear and interacting effects of fire severity and time since fire is important to fully understanding post-wildfire responses for a majority of birds. Moreover, the study supports a growing body of literature that indicates mixed-severity fire is essential for conserving avian diversity in many fire-maintained systems.

SummaryRecent evidence indicates that insectivorous birds in shade coffee farms provide economically significant ecosystem services by reducing insect pests, which should encourage cultivation practices favouring birds and other wildlife. However, the provisioning of this service may be dependent on landscape composition and movement patterns of these mobile consumers. Very little information is currently available on bird movements in coffee-dominated landscapes. We examined roosting behaviour in Black-throated Blue Warblers Dendroica caerulescens on two Jamaican coffee farms using radio telemetry in order to determine whether birds commute between nocturnal roosts and diurnal foraging ranges in coffee habitat. Nocturnal tracking revealed most birds moved outside diurnal foraging ranges on the farms to roost in forested habitat patches, sometimes up to 1 km away. Of 42 roost locations, only eight roosts were within the coffee farm perimeter: one individual in a coffee bush, and seven others in shade trees or vegetated riparian strips. Logistic regression confirmed that birds strongly selected continuous forest and individual trees over coffee for roosting. These findings reflect the ecological connectivity between coffee habitats and the adjacent landscape and raise the possibility that the provisioning of pest reduction services could be at least partly dependent on a farm's proximity to forest patches.

Disturbances alter biodiversity via their specific characteristics, including severity and extent in the landscape, which act at different temporal and spatial scales. Biodiversity response to disturbance also depends on the community characteristics and habitat requirements of species. Untangling the mechanistic interplay of these factors has guided disturbance ecology for decades, generating mixed scientific evidence of biodiversity responses to disturbance. Understanding the impact of natural disturbances on biodiversity is increasingly important due to human-induced changes in natural disturbance regimes. In many areas, major natural forest disturbances, such as wildfires, windstorms, and insect outbreaks, are becoming more frequent, intense, severe, and widespread due to climate change and land-use change. Conversely, the suppression of natural disturbances threatens disturbance-dependent biota. Using a meta-analytic approach, we analysed a global data set (with most sampling concentrated in temperate and boreal secondary forests) of species assemblages of 26 taxonomic groups, including plants, animals, and fungi collected from forests affected by wildfires, windstorms, and insect outbreaks. The overall effect of natural disturbances on α-diversity did not differ significantly from zero, but some taxonomic groups responded positively to disturbance, while others tended to respond negatively.

Ultrasonic telemetry was used to analyze the effects of environmental variables on movement directions and movement rates of brown smoothhounds, Mustelus henlei, in Tomales Bay, California. Ultrasonic transmitters were surgically implanted in the peritoneal cavities of one male and five female brown smoothhounds and tracked during the period of 29 June to 15 July 2004. Coarse-scale tracking consisted of locating all tagged individuals multiple times during a single session, while fine-scale tracking consisted of following a single individual continuously during a session. Coarse-scale tracking suggested movement toward the inner bay with incoming and high tides and toward the outer bay with outgoing and low tides (P = 0.01), whereas the diel cycle had no apparent effect on their movement directions. Mean shark movement rate was 0.09 m s −1 (range: 0.01-0.34 m s −1 ), with diel and tidal cycles both having significant effects on their rates of movement (P = 0.02 and P<0.01), respectively. We tracked two female sharks on a fine scale over three tracking sessions in July 2004. Both individuals exhibited higher rates of movement during the night compared to the day (P<0.01). While one shark's rate of movement was not significantly affected by tidal stage, the other's was (P<0.001).